Various errors may occur in the intake tract of an internal combustion which impair the performance of the engine and/or result in increased exhaust gas emissions. To correct these errors, the error that is actually present must be identified within the scope of a repair shop diagnosis. Leaks in the intake tract of the internal combustion engine which are caused by small holes or loose clamps are particularly difficult to detect and to distinguish from other errors.
Conventionally, for diagnosing the air supply system of an internal combustion engine, the mass flow into the intake tract is measured and compared to a theoretical computed mass flow. The presence of an error in the intake tract may be deduced based on the magnitude of the deviation of the measured mass flow from the theoretical computed mass flow. However, it is generally not possible to use this procedure to distinguish between various types of errors, for example an error caused by a leak in the intake tract versus some other error, for example caused by a defective valve, a slipped toothed belt, or a defective mass flow sensor.